platform/x86: asus-wmi: add keystone dongle support

The ASUS Keystone is a physical NFC-like dongle that slots into supported
ASUS laptops. The EC fires WMI notify code 0xB4 on insert/remove events.

Expose the current insert state via a sysfs attribute by querying WMI
device ID 0x00120091 (DSTS). This devid does not follow the standard DSTS
convention: PRESENCE_BIT (0x00010000) encodes the insert state rather than
feature presence, and STATUS_BIT is never set. Presence of a keystone slot
is detected by a successful DSTS call.

Reviewed-by: Denis Benato <denis.benato@linux.dev>
Signed-off-by: Dariusz Figzał <dariuszfigzal@gmail.com>
Link: https://patch.msgid.link/20260610164942.74956-1-dariuszfigzal@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/Documentation/ABI/testing/sysfs-platform-asus-wmi b/Documentation/ABI/testing/sysfs-platform-asus-wmi
index 89acb6638df8a59629c4857cefec14e380a44255..f9825c6150b5c0732b1641a43943ffcf15f00b3b 100644 (file)
--- a/Documentation/ABI/testing/sysfs-platform-asus-wmi
+++ b/Documentation/ABI/testing/sysfs-platform-asus-wmi
@@ -58,6 +58,15 @@ Description:
                        * 1 - overboost,
                        * 2 - silent
 
+What:          /sys/devices/platform/<platform>/keystone
+Date:          Jun 2026
+KernelVersion: 7.2
+Contact:       "Dariusz Figzał" <dariuszfigzal@gmail.com>
+Description:
+               Reports the Keystone dongle insert state (read-only):
+                       * 0 - not inserted
+                       * 1 - inserted
+
 What:          /sys/devices/platform/<platform>/gpu_mux_mode
 Date:          Aug 2022
 KernelVersion: 6.1

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 80144c412b902f33811da48fe0433092678cb928..3c9ef826551d3fb2690d71c86b3e3cb271819377 100644 (file)
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -70,6 +70,7 @@ module_param(fnlock_default, bool, 0444);
 #define NOTIFY_KBD_TTP                 0xae
 #define NOTIFY_LID_FLIP                        0xfa
 #define NOTIFY_LID_FLIP_ROG            0xbd
+#define NOTIFY_KEYSTONE                        0xb4
 
 #define ASUS_WMI_FNLOCK_BIOS_DISABLED  BIT(0)
 
@@ -279,6 +280,8 @@ struct asus_wmi {
        u32 tablet_switch_dev_id;
        bool tablet_switch_inverted;
 
+       bool keystone_available;
+
        enum fan_type fan_type;
        enum fan_type gpu_fan_type;
        enum fan_type mid_fan_type;
@@ -646,6 +649,55 @@ static bool asus_wmi_dev_is_present(struct asus_wmi *asus, u32 dev_id)
        return status == 0 && (retval & ASUS_WMI_DSTS_PRESENCE_BIT);
 }
 
+/* Keystone *******************************************************************/
+
+static int keystone_check_present(struct asus_wmi *asus)
+{
+       u32 retval;
+       int err;
+
+       asus->keystone_available = false;
+
+       /*
+        * Use a raw devstate call rather than asus_wmi_dev_is_present().
+        * For this devid, PRESENCE_BIT encodes current insert state, not
+        * feature presence, so asus_wmi_dev_is_present() would return false
+        * whenever the dongle is absent at boot, even on machines that have
+        * a keystone slot.
+        * -ENODEV means the firmware doesn't know this devid at all.
+        * retval is not examined here, only the return code matters.
+        */
+       err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_KEYSTONE, &retval);
+       if (err == -ENODEV)
+               return 0;
+       if (err)
+               return err;
+
+       asus->keystone_available = true;
+       return 0;
+}
+
+static ssize_t keystone_show(struct device *dev,
+                            struct device_attribute *attr, char *buf)
+{
+       struct asus_wmi *asus = dev_get_drvdata(dev);
+       u32 retval;
+       int err;
+
+       err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_KEYSTONE, &retval);
+       if (err)
+               return err;
+
+       return sysfs_emit(buf, "%d\n", !!(retval & ASUS_WMI_DSTS_PRESENCE_BIT));
+}
+
+static DEVICE_ATTR_RO(keystone);
+
+static void asus_wmi_keystone_notify(struct asus_wmi *asus)
+{
+       sysfs_notify(&asus->platform_device->dev.kobj, NULL, "keystone");
+}
+
 /* Input **********************************************************************/
 static void asus_wmi_tablet_sw_report(struct asus_wmi *asus, bool value)
 {
@@ -4575,6 +4627,12 @@ static void asus_wmi_handle_event_code(int code, struct asus_wmi *asus)
                return;
        }
 
+       if (code == NOTIFY_KEYSTONE) {
+               if (asus->keystone_available)
+                       asus_wmi_keystone_notify(asus);
+               return;
+       }
+
        if (code == NOTIFY_KBD_FBM || code == NOTIFY_KBD_TTP) {
                if (asus->fan_boost_mode_available)
                        fan_boost_mode_switch_next(asus);
@@ -4698,6 +4756,7 @@ static struct attribute *platform_attributes[] = {
        &dev_attr_lid_resume.attr,
        &dev_attr_als_enable.attr,
        &dev_attr_fan_boost_mode.attr,
+       &dev_attr_keystone.attr,
 #if IS_ENABLED(CONFIG_ASUS_WMI_DEPRECATED_ATTRS)
                &dev_attr_charge_mode.attr,
                &dev_attr_egpu_enable.attr,
@@ -4741,6 +4800,8 @@ static umode_t asus_sysfs_is_visible(struct kobject *kobj,
                devid = ASUS_WMI_DEVID_ALS_ENABLE;
        else if (attr == &dev_attr_fan_boost_mode.attr)
                ok = asus->fan_boost_mode_available;
+       else if (attr == &dev_attr_keystone.attr)
+               ok = asus->keystone_available;
 
 #if IS_ENABLED(CONFIG_ASUS_WMI_DEPRECATED_ATTRS)
        if (attr == &dev_attr_charge_mode.attr)
@@ -5081,6 +5142,10 @@ static int asus_wmi_add(struct platform_device *pdev)
        if (err)
                goto fail_platform_profile_setup;
 
+       err = keystone_check_present(asus);
+       if (err)
+               dev_warn(&pdev->dev, "Failed to check Keystone presence: %d\n", err);
+
        err = asus_wmi_sysfs_init(asus->platform_device);
        if (err)
                goto fail_sysfs;

diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
index 554f41b827e18a7f0b811203d5cbbbe335817411..c29962d5baac6492bcc4d47f5cb51d1366556eff 100644 (file)
--- a/include/linux/platform_data/x86/asus-wmi.h
+++ b/include/linux/platform_data/x86/asus-wmi.h
@@ -147,6 +147,13 @@
 #define ASUS_WMI_DEVID_GPU_MUX         0x00090016
 #define ASUS_WMI_DEVID_GPU_MUX_VIVO    0x00090026
 
+/* Keystone dongle insert/remove state.
+ * PRESENCE_BIT (0x00010000) encodes insert state:
+ * 0x00010000 = inserted, 0x00000000 = absent. STATUS_BIT is never set.
+ * 0xFFFFFFFE means no keystone slot on this machine.
+ */
+#define ASUS_WMI_DEVID_KEYSTONE                0x00120091
+
 /* TUF laptop RGB modes/colours */
 #define ASUS_WMI_DEVID_TUF_RGB_MODE    0x00100056
 #define ASUS_WMI_DEVID_TUF_RGB_MODE2   0x0010005A